All subjects will be required to provide their informed consent prior to enrolling in the study. Individuals will be screened for study eligibility according to the exclusion criteria, as followed: 1) no antibiotic medications or drugs known to influence fecal microbiota were taken 3 mo before the study; 2) active treatment for doctor diagnosed diseases, such as cancer, cardiovascular diseases, gastrointestinal diseases; 3) regular use of any dietary supplements; 4) colonoscopy 2 mo prior to their enrollment or scheduled during the study; 5) values of standard blood biochemistries are critically abnormal based on study physician's discretion; and 6) use of ≥14/wk serving of alcohol. Subjects who meet all other eligibility criteria and have values of blood biochemistries within normal ranges will be asked to participate in the study.